Abstract

We demonstrate crystals (LiNbO3-like) that were space-selectively nucleated and grown in the bulk of silica-based glass by femtosecond laser irradiation at a high repetition rate (typ. 300 kHz). Oriented crystals with their polar axis mostly aligned with or perpendicular to the laser scanning direction have been fabricated by manipulation of the temperature gradient in adjusting the laser parameters. The mechanism for the orientation of femtosecond laser-induced crystallization is briefly discussed.

Figures (3)

SEM image (a) EBSD map, (b) Kikuchi pattern, (c) cross section of a line after cleaving, polishing, and etching. Other laser parameters: 300 kHz, 5μm/s. The colors in EBSD map based on R3c space group and LiNbO3 crystal parameters indicate the crystal axis, which is perpendicular to the image plan.

(a) Second-harmonic microscopy images of two lines in each group written at different pulse energies. (b) Polarization dependence of SH intensity of the written lines at 1.2 μJ (red) and 1.5 μJ (blue) as a function of probe polarization angle, the line direction is at 90°.

Calculation of the temperature field and of the thermal gradient distribution under scanning in the middle depth of the volume interaction 0.6(Li2ONb2O5)-0.4SiO2 glass for pulse energy of 1.5μJ/pulse, scanning speed of 100μm/s to the right-hand side and repetition rate of 300 kHz. The figure on the left is the whole T field that shows elliptical shape of the isotherms. The T range around 750 K should be considered for growth (light blue) between two yellow circles. Regions 1 and 2 in the text are included between the two lines.